A top choice...Linux, MacOS X and Windows versions available! The free version can make 3"x4" single-sheet boards, which suffices for hobby/research/educational layouts and designs. The non-commercial license is also quite cheap & doubles the max PCB size.
An open source EDA suite thats in the works. Some people swear by it. I'm not a convert yet but I'm keeping close watch.
- PCB Express / PCB123
This PCB company gives out 'free software' for PCB layout. However, it has strings attached: the files are saved in a proprietary format & you cannot export Gerber files from it (unless you pay them for the 'privilege'). This means you will forced to use PCB123 every time you make PCBs from your design. For that reason I think its a terrible idea: there's other software that doesn't lock you into a manufacturer and theres a good chance you'll regret going with them if you want to go beyond a prototype.
After talking with marketing representatives from the company it seems clear to me that the software isn't better than Eagle, their prices are higher than 4pcb's, and thus they have to 'trick' people into using their service. Lame!
- KiCAD (Must research)
- Protel (Popular in industry)
Sadly, it's at End of Life (discontinued)
Incase you were wondering, all CAD software sucks. The UI's on all of them are horrific to anyone used to quality software. It's not clear why this is but they're all bad in different but equally-annoying ways. That's just how it is.
Also, unless you spent $10K on your software, the autorouter is worthless. Take the time to route your own boards, you'll find it worth doing! Edit: I got pointed at http://www.freerouting.net/, very interesting, you can use an online board router?
A gerber viewer is essential to checking your PCBs before shipping!
- There's an open source viewer called gerbv
- GC Prevue from GraphiCode is free for viewing (Windows only)
You can send your files over to FreeDFM for basic design for manufacturability (DFM) tests